91 Ranger 4.0 lacks power

[danike]

4.0 engine that was running fine but once in a while would miss on start up for 10 to 20 seconds. One day it ran bad for 2.5 miles then ran fine and that became the norm for a month until now it runs bad all the time. Seems like it is lacking power or out of time. Checked the wires and plugs. Spark jumping out of towers to wires. Had ignition module tested at Autozone OK. Codes 21 and 24 came up when problem is present, replaced the coolant temp. sensor and air temp. sensor no change. Tried a crank position sensor. Have 4.6 volts going to the coolant and air temp. sensor. My book shows alternate meanings for the code 21 and 24 such as crank position circuit and primary circuit in coil. Any ideas or solutions?

[mrshorty]

Were the 21/24 KOEO codes? A common cause of KOEO 21/24 (especially together) is performing the test on a cold engine. The computer expects to see the temperature sensors above a certain threshold temperature.

What does fuel pressure look like?

[danike]

Fuel pressure was 32 or 38 psi. The codes did go away when the engine was warmed up and running properly. Don't remember if i check the codes warm and running bad.